Insulator.



UNITED STATES PATENT OFFICE.

LAWRENCE E. BARRINGER, OF SCHENECTA DY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

INSULATOB.

No Drawing.

Specification of Letters Patent. Patented Mar. 31, 1914.: Applicationfiled May 14, 1808. Serial No. 432,908

To all whom it may concern Be it known that I, LAWRENCE E. BAR- nmonn, acitizen of the United States, residing at Schenectady, county ofSchenectady, State of New'York, have invented certain new and usefulImprovements in Insulators, of which the following is a specification.

My present invention comprises a new insulating material for use in theelectrlcal arts, possessing many valuable characteristics, andmanufactured by a novel process, simple and inexpensive in character.

According to my process of manufacture, a hydrate such as sla'ked limeis mtimately mixed with silica, either with or without the addition offibrous material, such as asbestos, and the mixture so formed is steamtreated to form a firm, dense insulator.

Although the proportions of the several ingredients may be variedthroughout a considerable range, I aim to keep the hydrate in suchexcess that the steam treated article still contains some free hydrate.

The following is a suitable composition: Slaked lime parts, flint 20parts, asbestos 20 parts- The lime should be completely slaked, and theflint should referably be clean and finely powdered. T e mixture ismoistened with water, pressed into the desired shapes, such as plates,tubes, blocks, etc., then dried, and finally subjectedjto a treatmentwith dry steam at a pressure of about 150 pounds. The duration of thesteam treatment depends somewhat on the size and shape of the pressedbodies, but a period of six hours is suitable for small plates. Thesteamin action causes practically complete com ination of the flintwithpart of the lime to form hydrous-calcium silicate, leavinguncombined, a certain per cent. of the soft calcium hydrate. Thus in thefinished product there is hydrous-calcium silicate, asbestos fiber, andsoft calcium hydrate; but no free flint or other gritty material. Theproportion of silicate, the chief binding material, is comparativelysmall, but nevertheless the product is hard, firm, and strong enough topermit machining, as in a lathe or drill press. The absence of any freeflint or other gritty material insures little wear on the machiningtools. Similarly, the use of such a small proportion of flint in the rawmixture insures little wear on the steel molds by which the mixture isshaped into plates, tubes, etc.

In a certain sense, this composite insulator, consisting of asbestos anda free bydrate, held together by hydrous-calcium silicate, may, aftermachining, be regarded as finished and complete. It happens, however,that in the course of time, the free hydrate will change over, byexposure to air, into a carbonate, thereby giving to the insulatingmaterial greater strength and hardness. Thus, while the material may beeasily machined just after manufacture, it increases in hardness to suchan extent that after some time has elapsed it cannot be cut or machinedexcept with difliculty.

It should be noted that the presence of free hydrate of calcium, or itsequivalent, permits impregnation of the insulator with substances whichenter into chemical combination and thereby form products which stay inthe insulator and form part thereof. For instance, if the steam treatedbody is impregnated with rosin oil, a combination takes place betweenthe terpenes of the oil and the calcium hydrate, forming a solid mass,This impregnation renders the material waterproof, but what is moreimportant, does so by means of a filler produced in the pores of thematerial more stable than the rosin oil, and .not liable to melt out,even when heated to the tempernture at which the rosin oil wasintroduced.

In place of rosin oil as an impregnating material, I may use linseedoil, in which case partial saponification of the oil by the free calciumhydroxid ensues. Or melted stearic acids may be used to impregnate thecom? pound, the treatment resulting in the formation of calcium stearatein the pores of the compound. Similarly, the formation of an oleate orpalmitate may be produced in the pores of the material.

From what has been stated, it will be seen that the original or rawmixture is such that it can be molded to the desired shape in steel dieswith very little wear on the dies;

that it can be hardened by steam treatment to form a material which isdense and strong, but which nevertheless can be machined or cut toany"desired shape without rapidly wearing away the cutting tools; thatthe composition is such that after manufacture to the desired form itbecomes harder with age; and that the composition is such that duringthe process of impregnating with diiferent substances to produce awaterproof condition a part of the material will react with theimpregnating substances to form compounds of higher melting point andgreater stability. All of-these characteristics are of great importance,rendering my improved product most suitable for extensive commercialapplicationas'an electrical insulator.

What I claim as new and desire to secure.

molding .it. into shape, v treating with steam under pressure toproduce-chemical union between the silica and the 'calcium'hydrate,machining the body'so formed, an

cium hydrate into a lime soap.

3. The method which-consists in mixing silica with a substantial excessof calc um with live steam under pressure to effect a d subsequentlyconverting its excess of cal reaction bet-ween the silica and hydrate,and

subsequently impregnating "the material so produced with stearic'acid toform stearate of calcium in the mass'by interaction with the freecalcium hydrate.

4. A material suitable for electrical insulators and the like consistingessentially of asbestos, hydrous calcium silicate and lime soap.

In witness whereof, I have hereunto set my hand this 13th day of May,1908.

LAWRENCE E. BARRINGER.

Witnesses BENJAMIN B. HULL, HELEN- ORFORD- Copies of this patent may beobtained for five cents each, by addressing the Commissioner of Patents.

Washington, D. G.

